Endoscopic surgical instruments are often preferred over traditional open surgical devices since the use of a natural orifice tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a working end of a tool at a desired surgical site through a natural orifice. These tools can be used to engage and/or treat tissue in a number of ways to achieve a diagnostic or therapeutic effect.
One tool commonly used in endoscopic surgery is a surgical stapler and cutter, which typically includes an end effector that simultaneously makes a longitudinal incision in tissue and applies lines of staples on opposing sides of the incision. The end effector includes a pair of cooperating jaw members that are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil. The instrument also includes a knife that cuts the stapled tissue.
Surgical staplers/cutters continue to increase in complexity and function with each generation due to the desire to introduce the devices endoscopically. However, endoscopic surgery requires that the shaft of the device be flexible while still allowing the end effector to be articulated and/or rotated to angularly orient the end effector relative to the tissue, and to be actuated to close the end effector and fire the staples. Integration of the controls for articulating, rotating, and/or actuating an end effector tend to be complicated by the use of a flexible shaft and by the size constraints of an endoscopic instrument. Generally, the control motions are all transferred through the shaft as longitudinal translations, which can interfere with the flexibility of the shaft.
There is also a desire to lower the force necessary to actuate the end effector to a level that all or a great majority of surgeons can handle. One known solution to lower the force-to-fire is to use electrical motors. However, surgeons typically prefer to experience feedback from the end-effector to assure proper operation of the end effector. The user-feedback effects are not suitably realizable in present motor-driven devices.
Accordingly, there remains a need for improved methods and devices for controlling movement and actuation of an end effector on an endoscopic surgical device.